Control: 2.10 Ensure That the Log Metric Filter and Alerts Exist for Cloud Storage IAM Permission Changes

Description

It is recommended that a metric filter and alarm be established for Cloud Storage Bucket IAM changes.

Monitoring changes to cloud storage bucket permissions may reduce the time needed to detect and correct permissions on sensitive cloud storage buckets and objects inside the bucket.

Remediation

From Console

Create the prescribed log metric:

1. Go to Logging/Logs-based Metrics by visiting https://console.cloud.google.com/logs/metrics and click "CREATE METRIC".
2. Click the down arrow symbol on the Filter Bar at the rightmost corner and select Convert to Advanced Filter.
3. Clear any text and add:

resource.type="gcs_bucket"
AND protoPayload.methodName="storage.setIamPermissions"

4. Click Submit Filter. Display logs appear based on the filter text entered by the user.
5. In the Metric Editor menu on right,fill out the name field.Set Units to 1 (default) and Type to Counter. This ensures that the log metric counts the number of log entries matching the user's advanced logs query.
6. Click Create Metric.

Create the prescribed Alert Policy:

1. Identify the newly created metric under the section User-defined Metrics at https://console.cloud.google.com/logs/metrics.
2. Click the 3-dot icon in the rightmost column for the new metric and select Create alert from Metric. A new page appears.
3. Fill out the alert policy configuration and click Save. Choose the alerting threshold and configuration that makes sense for the user's organization. For example, a threshold of zero(0) for the most recent value will ensure that a notification is triggered for every owner change in the project:

Set `Aggregator` to `Count`
Set `Configuration`:
- Condition: above
- Threshold: 0
- For: most recent value

4. Configure the desired notifications channels in the section Notifications.
5. Name the policy and click Save.

From Command Line

Create the prescribed Log Metric:

• Use the command: gcloud beta logging metrics create

Create the prescribed Alert Policy:

• Use the command: gcloud alpha monitoring policies create